<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <!-- select标签的value是选中的option的value -->
  <select>
    <option value="1">北京</option>
    <option value="2">上海</option>
    <option value="3">广州</option>
    <option value="4">航头</option>
  </select>
  <script>
    const sel = document.querySelector('select')
    sel.addEventListener('change',(e)=>{
      console.log(e.target.value);
    })
  </script>
</body>
</html>